Webhooks
In addition to retrieving shipment updates via the GET APIs you can receive them by webhook PUSH. A webhook is an endpoint hosted by you that you have registered to receive shipment updates on. When you have a webhook configured, changes to your shipments will be sent (pushed) to your hosted endpoint via HTTP request as a request body using the same format as the JSON response body for the Get Full Tracking History endpoint: /api/v4/shipments/{shipmentId}/tracking/history.
Each new event message includes all events related to the shipment. For position updates, only the latest is included in each new message.
For full details on creating a webhook see the Webhook Guide.